Aspirin is being studied as a colorectal cancer chemopreventive. Our previous work suggested that aspirin plasma pharmacokinetics did not correlate with suppression of colorectal tissue prostaglandins. The purpose of this trial is to determine whether tissue concentrations of aspirin and salicylic acid reflect plasma concentrations or reflect colorectal tissue prostaglandin content. We hypothesize that colorectal tissue aspirin and salicylic acid concentrations will reflect plasma concentrations.